Inconsistent DVD accessibility

[MR ZenWiz]

I've brought this up before, but I haven't seen a solution and I'm
hoping this information may help.

I run Xubuntu 14.04.4 with the 4.2.0-38 kernel on my home desktop, up
to date from a base 14.04.1 install.  It has an Intel i7 CPU and 16GB
of main memory.  The machine also has a Blu-ray DVD burner and an
HD-DVD burner, both SATA.

I also have an HP8710 laptop with an Intel Core 2 Duo and 4GB of
memory, running 14.04.4 with the standard kernel (3.13.something).
This machine has one of the old DVD burner slide trays.

I have purchased a couple of mass-market DVDs lately that behave as
follows (both of them, consistently):

My desktop does not recognize them as readable media and refuses to
mount or provide any access to them.

My laptop can read them, play them, and I have used K3B to rip them
both to ISO images.

The ISO images both play and run properly, including all the menus and
features on the laptop.

The ISO images (copied vi alfash drive to the desktop) play on the
desktop, but the menus and images don't work right.  E.g., I can't set
subtitles to work, and on one of them, the built-in subtitles for
foreign language pieces of the movie work fine on the laptop but not
on the desktop (from the images - the disks do not work at all on the
desktop - only).

The hardware in the laptop is form back in the 90s, whereas the
hardware in the desktop is all less than two years old.

What are the possibilities here?  Is this a DRM issue (and how does
one sidestep that insane garbage)?  Is it maybe the different kernels?
 Is this simply a hardware issue (old vs. new optical burner drives)?

Thanks.
MR